In the field of electronically controlling traction systems for rail vehicles, it is known to use electronic units that operate in real time and that are designed to control electronic circuits such as gate turnoff (GTO) thyristors or insulated gate bipolar transistors (IGBT), low voltage relays, or digital or analog indicators. Such units include a computer suitable for generating control signals as a function of signals received at inputs of the unit, said input signals possibly being a reference value, signals representative of the state of a low voltage relay, signals representative of a current, of a voltage, or of power consumption, and/or signals issued by an on-board computer network. In order to control electronic circuits of the GTO or IGBT type effectively, the control signals issued by such an electronic unit must be positioned in time with precision of microsecond order.
Since such a control unit constitutes a complex piece of equipment, it is known to provide a test bench having a simulator suitable for generating simulated signals which are supplied to the inputs of the unit, and to analyze the control signals generated by such a unit. Such a simulator operates in real time and simulates, for example, the motor, the brakes, or the inertia of a rail motor unit, and also simulates the state of the rails or other external parameters. A single type of simulator is used for testing the operation of various different electronic units, with the operation of the simulator being adapted by being programmed as a function of the type and the purpose of the unit. Such a simulator comprises one or more microprocessors for processing signals issued by the unit so as to send new simulation signals thereto. Such a simulator is of the type which includes hardware in the loop.
Unfortunately, given the computer processing they need to perform, simulation programs operate with a cycle time of the order of several tens of microseconds, said cycle times being much greater than the precision desired of the electronic unit, which precision is of microsecond order. In other words, when it has acquired a signal generated by the unit to be inspected, the microprocessor or computer works “blind” for several tens of microseconds before generating a new simulation signal. Consideration might be given to interrupting the operation of the microprocessor frequently, e.g. once every microsecond, so as to acquire a new value of the signal issued by the unit, however that would significantly disturb the operation of the computer which could no longer deal with the numerous values acquired. In addition, such a solution is not technically feasible when the desired precision is itself of microsecond order.